Which API assigns labels to images and classifies them into predefined categories?

The Vision API is designed specifically to analyze images and assign labels based on the content it identifies. It is capable of recognizing a wide variety of objects and scenes, thereby allowing users to classify images into predefined categories. This functionality is particularly useful for applications that need to automatically tag images or organize visual content based on recognized features.

In contrast, the other options serve different purposes: the Translation API focuses on converting text from one language to another; the Speech-to-Text API is used to convert spoken language into written text; and the Natural Language API processes text to understand its structure and meaning. Each of these APIs addresses specific tasks within natural language processing, audio transcription, or translation, rather than image classification and labeling as the Vision API does.